1. Field of the Invention
The present invention relates to an apparatus for adjusting or controlling an operating speed of a fluid-driven equipment such as pneumatic valve and pneumatic actuator driven by a compressed air by means of an orifice.
2. Related Art Statement
On-off valves driven by a compressed air have been widely used in supply conduits and discharge conduits of various kinds of liquids. In such a system, when the on-off valve is driven rapidly, a well-known water hammer phenomenon occurs. When the water hammer phenomenon occurs, not only undesired noise and vibration are generated, but also the valve might operate erroneously and a liquid might leak. In order to avoid such a water hammer phenomenon, there has been proposed to use a needle type speed control vale. Furthermore, in order to adjust the operating speed of the on-off valve, a coupling with an orifice having a fixed aperture size has been installed in a fluid path at an upstream position with respect to the valve.
In case of using the needle type speed controlling valve, although it is possible to perform a fine adjustment in an analog manner, the number of adjusting operations is large, and thus the adjusting operation could not carried out efficiently.
When the above mentioned coupling with an orifice having a fixed aperture size is used, it is necessary to exchange the coupling in order to change the operating speed of the on-off valve arranged at a downstream position with respect to the coupling. This requires the increased number of labor works and a plural kinds of couplings have to be stocked.